There are a limited number of metals in nature from which to choose materials for the fabrication of useful articles. A particular metal may have highly desirable properties in some respects coupled with unsatisfactory properties in othe respects. Frequently, for example, a metal which may be desirable for a particular application because of its lightness, cheapness, ease of fabrication, or resistance to corrosion may be unsuitable because it is too soft.
Historically, and even prehistorically, the problem has been handled through alloying; and the invention of bronze, an alloy of copper and tin is regarded as a major milestone in the development of civilization.
In alloys, however, the improvement in certain properties is frequently accompanied by impairment of other properties. Furthermore, it may be desired to improve the hardness of the alloys, themselves.